1. Field of the Invention
The present invention relates to a lighting optical system suitable for use in a projection apparatus such as a liquid crystal projector or the like.
2. Description of the Related Art
A lighting optical system is used for a projection apparatus such as a reflection type liquid crystal display apparatus. The reflection type liquid crystal display apparatus has: a light source for emitting the light such as a lamp; a reflector constructed of a concave reflecting device shaped like a cup, for reflecting the light emitted from the light source; a first integrator lens unit having a plurality of micro lenses, which are arrayed in a matrix, for example a 4.times.5 matrix, for dividing the light reflected by the reflector; a second integrator lens unit having a plurality of micro lenses, which are arrayed in a matrix in correspondence with each of the micro lenses of the first integrator lens unit, for superposing the lights divided by the first integrator lens unit; a condenser lens for condensing the lights passing through the micro lenses of the second integrator lens unit; and a display panel constructed of a liquid crystal display unit.
Further, the light source is disposed in the bottom side of the reflector shaped like a cup, namely, the back side of the light source is surrounded with the inner concave surface of the reflector. Further, the light source is disposed at the center of the reflector. The reflector spreads out like a cup toward the first integrator lens unit. The first integrator lens unit is disposed in front of the light source and the reflector at a distance. The second integrator lens unit is disposed in front of the first integrator lens unit at a distance. The condenser lens is disposed in front of the second integrator lens unit at a distance. The display panel is disposed in front of the condenser lens at a distance.
In operation, the light irradiated from the light source is emitted in the inner concave surface of the reflector, and the reflected light is irradiated into the first integrator lens unit. At this time, the reflected light is divided into a plurality of lights respectively corresponding to the micro lenses of the first integrator lens unit. Namely, the reflected light is divided into a plurality of lights in a matrix-like manner by the micro lenses disposed in the first integrator lens unit. Then, each of the divided lights is irradiated into the micro lenses disposed in the second integrator lens unit, and the divided lights are condensed and superposed by the micro lenses disposed in the second integrator lens unit. Further, superposed lights are condensed by the condense lens and the condensed lights are irradiated into the display panel.
In this manner, the light emitted from the light source is divided by the first integrator lens unit, and the divided lights are superposed by the second integrator lens unit, so that the uniform light can be irradiated into the display panel. Thus, the brightness of the display panel can be made uniform.
However, as mentioned above, the light source is disposed in the bottom side of the reflector shaped like a cup. Namely, the light source is disposed between the bottom portion of the reflector and the first integrator lens unit. Further, the light source is positioned on the axis between the central portion of the reflector and the central portion of the first integrator lens unit. Therefore, when the light is emitted form the light source and reaches the first integrator lens unit, the light irradiated into the first integrator lens unit is affected by the components of the light source at the center portion of the first integrator lens unit. Namely, the component of the light source obstructs the progression of the light, which is emitted from the light source and reaches the first integrator lens unit. As a result, the intensity of the light irradiated into the center portion of the first integrator lens unit is different from that of the light irradiated to other portions of the first integrator lens unit. Thus, the micro lenses disposed at the center portion of the first integrator lens unit are affected by the components of the light source.
As a result, a shadow of the components of the light source appears in the display panel. Therefore, it may happen a case that non-uniformity of luminous intensity and non-uniformity of color appear in the display panel, and the quality of display is degraded.
Further, the light source has a lead wire for supplying power and controlling the light. This lead wire connects the light source disposed in the reflector shaped like a cup and a power supply disposed at the out of the reflector to each other. Further, the reflector has a wiring hole in order to lead the line wire toward the out side thereof. This wiring hole is disposed near the center portion of the bottom side of the reflector. Therefore, the light irradiated to the first integrator lens unit is affected by the lead wire and the wiring hole. Namely, shadows of each of the lead wire and the wiring hole appear in the display panel. Thus, it may happen that non-uniformity of luminous intensity and non-uniformity of color appear in the display panel, and the quality of display is degraded.